Node.js Design Patterns - Second Edition

Asynchronous control flow with streams

Going through the examples that we have presented so far, it should be clear that streams can be useful not only to handle I/O, but also as an elegant programming pattern that can be used to process any kind of data. But the advantages do not end at the simple appearance; streams can also be leveraged to turn the asynchronous control flow into flow control, as we will see in this section.

Sequential execution

By default, streams will handle data in a sequence; for example, a _transform() function of a Transform stream will never be invoked again with the next chunk of data, until the previous invocation completes by executing callback(). This is an important property of streams, crucial for processing each ...